EE WAS OPERATING A HAULTRUCK WHILE THE TRUCK WASBEING LOADED, A LG. ROCK FELL OUT OF THE SHOVEL BUCKET AND INTO THE TRUCK BED. THIS CAUSED THE CAB TO JERK AND THE EE REPORTED HE BUMPED HIS HEAD ON THE SEATS HEADREST. EE LATER COMPLAINED OF HEADACHE, DIZZINESS, CONFUSION. 1ST SAW DR. ON 1-25-02. CAT SCAN SHOWED A CEREBRALMASS. ORDERED MRI TO CONFIRM. RESULTS IN A FEW DAYS.